The relative mRNA expression levels of ER stress markers GRP78 (1.67 ± 0.28), CHOP (4.0 ± 0.61) and spliced XBP1 (1.85 ± 0.85) were elevated in primary AEC obtained from IPF patients compared to healthy controls. The gene discussed is XBP1; the disease is idiopathic pulmonary fibrosis.